What happens if a library containing zero or one card is shuffled?

When a library containing zero or one card is shuffled, abilities that trigger on shuffle still trigger. This is because the act of shuffling the library is defined as a specific action that occurs regardless of the number of cards in the library. The rules state that shuffling a library does not have any requirements regarding the number of cards it contains; thus, when a library is shuffled, it will trigger any relevant abilities associated with the shuffle action.

For example, if a card has an ability that states, “When you shuffle your library,” this ability will trigger even if there are no cards to rearrange. This demonstrates that the shuffle event itself is what prompts the triggering, not the number of cards present. Therefore, the correct answer accurately reflects this aspect of the game's rules concerning shuffling libraries.